Free pdf of same article:
https://www.researchgate.net/public...sk_Measure_Anything_More_Than_Digit_SpanA few more points:
1. The study sample in the cited article was relatively modest (100 adults).
2. The study sample was not representative of the adult population, as they were mostly young, and mostly university students, who generally are above average. IOW, a convenience sample.
3. The scores reported for Digit Span are not the length of the longest span recited accurately, but the raw scores of the tasks, which, again, are administered in pairs, and don't necessarily increment one span unit at each item set, or start with the span length you expect.
The data seem fairly consistent with what I have already presented upthread, regarding the mean span length of adults, with perhaps a slight bias upward because of the study population. They actually did very slightly worse than would have been expected on digits backward--but then, it was a small data set, so that could have been chance variation based on the specific participants, and regardless, their mean scores were in the average range.
Interpreting neuropsychological research does require a little bit of field-specific background knowledge, so do be cautious about leaping to any conclusions based on a raw reading of a single journal article.
